PNEUMOCOCCUS I2Q 



are due to the toxins of the streptococcus ; cavity formation and hectic 

 fever for example. Its virulence can be intensified by passing it 

 through a series of animals, until, finally, y^Vfr of a cubic milli- 

 meter killed in one day all the mice injected' with this dose. The 

 toxin contains a peculiar haemolytic substance, which, as before 

 remarked, dissolves red cells of the blood, hence the anaemia in sep- 

 ticaemia and in suppuration. The toxin of the streptococcus, if in- 

 jected under the skin, causes redness like erysipelas. Coley's fluid 

 containing this toxin is used to treat sarcomata, since infection with 

 the streptococcus has been known to cause a disappearance of these 

 tumors. Practically all animals are susceptible to the streptococcus. 



Agglutinations. The serum from an animal injected with strep- 

 tococci, or immunized against it, will agglutinate streptococci. 



Anti-toxic sera have been prepared by injecting horses .with highly 

 virulent living culture of streptococci. The serum protects to a 

 limited degree, and has some curative properties. Cultures of cocci 

 from human sources have been found to produce the best toxins; 

 there are, however, many strains. 

 . 



PNEUMOCOCCUS. 



Streptococcus lanceolatus, commonly known as the pneu- 

 mococcus, or Diplococcus lanceolatus. (Fig. 39.) 



Morphology and Stains. This organism is usually found in the 

 tissues and sputum, in the form of lance-shaped cocci, surrounded 

 by a capsule. Is almost always associated in pairs, though some- 

 times in chains of five or six members. In albuminous fluids, or 

 blood serum, and in milk, the organism exhibits a well defined cap- 

 sule; in bouillon and other media, it loses the capsule and the lan- 

 ceolate shape, and often appears spherical, in pairs, or chains. It 

 is not motile, has no flagella or spores, is easily stained by all the 

 basic aniline dyes, and keeps its color by Gram's method. Under 

 certain conditions it strongly resembles the streptococcus pyogenes, 

 and may be differentiated therefrom by growing it on agar smeared 

 9 



